Chemically Bonded Phosphate-Based Bioceramics

CBPCs are excellent candidates for bioceramics for the following reasons  

Since bone contains mainly calcium phosphate compounds, and in particular HAP as the major mineral, calcium-based CBPC materials can provide the necessary bone composition. 

CBPCs may be placed as a paste or can be injected at the right place in a human body. It will harden rapidly after its delivery. It will attach itself to the adjacent surfaces and form a firm bond. The process is less intrusive as compared to hardened ceramics that need to be implanted surgically. 

Chemically bonded ceramics are more resorbable and surface reactive as compared to sintered counterparts. This is because they are more soluble within the body fluids as compared to the sintered ceramics. By controlling the composition, their solubility can be tailored to the desired value. 

The first feature discussed above has been well recognized, and much modern research has been focussed on developing biocompatible calcium-based ceramics. Manipulation of the microstructure, however, has not been attempted sufficiently, and much of the rapid prototyping has been to develop suitable macroscopic forms for sintered ceramics. 

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The chemically bonded bioceramics exhibit several properties suitable for in-situ in vivo placement in hard tissues. This is based on the chemical, physical and biological features of the biomaterials [4, 5-8]. The chemically bonded bioceramics - especially the materials based on phosphates, aluminates and silicates - exhibit a general nanostructure related to both the crystals and the... 

Chemically bonded ceramics constitute ceramics that are being formed due to chemical reactions. Often the precursor material is a ceramic powder (e.g. Ca-silicate or Ca-aluminate), which is "activated in a water-based liquid. A chemical reaction takes place in which the initial powder is partly or completely dissolved and new phases precipitate. The precipitated phases are composed of species from both the liquid and the precursor powder. The precipitates can be formed in situ in vivo, often in the nanoscale due to low solubility of the phases formed. The nanostructural chemically bonded bioceramics are especially found within the Ca-phosphate, Ca-aluminate and Ca-silicate systems. 

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